page won't display when I add the paypal form

<?php include("inc/products.php"); 


$product_id = $_GET["id"];
$product = $products[$product_id];

$section = "shirts";
$pageTitle = $product["name"];
include("inc/header.php"); ?>

            <div class="section page">

                <div class="wrapper"> 

                    <div class="breadcrumb"><a href="shirts.php">Shirts</a> &gt; <?php echo $product["name"]; ?></div>

                    <div class="shirt-picture">
                        <span>
                            <img src="<?php echo $product["img"]; ?>"  alt="<?php echo $product["name"]; ?>">
                        </span>
                          </div>

                            <div class="shirt-details">

                                <h1><span class="price">$<?php echo $product["price"]; ?></span> <?php echo $product["name"]; ?></h1>



        <form target="paypal" action="https://www.paypal.com/cgi-bin/webscr" method="post">
            <input type="hidden" name="cmd" value="_s-xclick">
            <input type="hidden" name="hosted_button_id" value="<?php echo $product["paypal]"; ?>">
            <input type="hidden" name="item_name" value="<?php echo $product["name"]; ?>">
            <table>
            <tr>
              <th>
            <input type="hidden" name="on0" value="Size">
            <label for="os0">Size</label>
              </th>
            <td><select name="os0" id="os0">
            <option value="Small">Small </option>
            <option value="Medium">Medium </option>
            <option value="Large">Large </option>
            <option value="X-Large">X-Large</option>
            </select> </td></tr>
            </table>
            <input type="submit" value="Add to Cart" name="submit">
        </form>


            <p class="note-designer">* All shirts are designed by Mike the Frog.</p>


                </div>

            </div>

        </div>



<?php include("inc/footer.php"); ?> ```